Operando DRIFT study of highly disperse CeO2 nanoparticles supported on MgO hexagonal plates during toluene oxidation

AGUIRRE, A.; FORNERO, ESTEBAN L.; BOSCO M.,; COLLINS, SEBASTIAN E.

Grindelwald

Congreso; Operando VII - the 7th International Congress on Operando Spectroscopy.; 2023

Paul Scherrer Institute

Operando DRIFT spectroscopy is used to identify the key reaction intermediates during toluene oxidationon highly disperse ceria nanoparticles deposited on MgO catalyst. Small CeO2 nanoparticles supported onmagnesium oxide hexagonal nanoplates showed enhanced catalytic performance to total toluene combustionas compared to a high surface area polycrystalline CeO2. Selective identification of active surface specieswas carried out by combining concentration-modulation excitation spectroscopy (c-MES) experiments withphase-sensitive detection (PSD) spectral analysis and a chemometric multivariate curve resolution alternatingleast squares (MCR-ALS) method. Toluene is molecularly adsorbed and reacts with surface oxygen to produceintermediate benzyl (C6H5CH2-) species. Next, benzyl is stepwise oxidized to benzyloxy/benzyl alcohol, benzaldehyde,and benzoate. The CeO2/MgO-h catalyst produces a higher amount of benzoate species than pureCeO2 during the toluene adsorption, while MgO-h oxidizes the toluene up to benzaldehyde. Later oxidation ofbenzoate and the aromatic ring produces formate and carbonate species. On pure CeO2, formates accumulateon the ceria surface and only a minor part of them reacts to produce CO2 (and CO). Instead, the formates arefast oxidized to CO2 on the CeO2/MgO-h catalyst and do not accumulate on the surface, due to the enhancedredox capacity and higher presence of oxygen vacancies (and peroxide/superoxide species) of the supportednanoparticles.